1. Field of the Invention
The present invention relates to a method in the manufacture of a keyboard for an electronic device. The invention also relates to an assembly for the manufacture of a keyboard for an electronic device.
2. Description of the Related Art
For storing various information, devices are available according to prior art, such as notepad computers, small hand-held computers, or PDA devices (Personal Digital Assistant). These devices can be used for storing e.g. calendar data, notes, address data, telephone numbers, or corresponding information entered by the user. The data are normally entered in these devices by means of a keyboard. Also wireless communication devices, such as mobile phones, comprise a keyboard an a display for storing or selecting telephone numbers. Known devices include Nokia 8110, 7110 and 6110 mobile phones. It is also known that devices are available which comprise a combination of two different user interfaces, for example the user interfaces of a mobile phone and a PDA device. One such known device is Nokia 9110 Communicator, whose first user interface is a PDA user interface and second interface is a CMT (Cellular Mobile Telephone) user interface for mobile station functions. The above-mentioned device comprises separate keyboards and displays for the different user interfaces in the opened and closed positions of the device, wherein the PDA user interface is on the inner surfaces of the two hinged housings of the device, and the CMT user interface is on the outer surface of one housing.
The size of PDA/CMT devices is particularly dependent on the thickness and size of the keyboard. A compact and light-weight structure is sought, wherein the device is easily portable. On the other hand, the different keys of the keyboard must travel accurately and give the user""s finger a clear feel of the operation both upon pressing and releasing the key. The feel is transferred by a click of the key which can be felt and often also heard. The click and the feel are produced in a known way by means of dome-shaped or bossed structures when they move in a buckling way, with a varying force required for the compression. In practice, the keys must not be located too close to each other, and they must be sufficiently large to make pressing with a finger possible and to prevent the pressing of an adjacent key. In the known PDA/CMT device, the key caps are fixed to a key pad made of rubber and positioned on a circuit board inside the device. The lower surface of the pad is provided with metal domes for clicking and electrical short circuiting. By the dome, the key pad is provided with a bulge to which the key cap is fixed. The keys extend through holes made in the housing of the device, and the housing also constitutes a frame protecting the key pad and the circuit board. Alternatively, the key cap can be fixed by a conical collar, whose buckling upon pressing of the key gives a feel of operation. The lower surface of the key is provided with a conductive material for short circuiting.
However, the structure according to prior art involves the problem that the frame structure, the key dome and the key cap constitute a relatively thick structure. Another problem is that the size of the key caps cannot be increased, because the frame necks would become too thin or narrow in view of the manufacture and strength. The necks are formed between holes and openings made in the frame structure. For this reason, the size of the keys must be limited, and they must be placed at a distance from each other, which also limits the design of the whole structure. For reasons related to the manufacturing technique and without weakening the structure, the frame structure cannot be made thinner without a limit to make the profile lower.
Yet another particular problem in the placing of the key caps on the key pad is caused by the fact that the mutual positioning of the key caps, fitting them in the same position and precisely at a desired distance from each other is a manufacturing stage requiring particular accuracy. In addition to the technical problem, variations in positions and rotation of the key caps in relation to each other and their turning in relation of the device and the keyboard give a poor impression of the whole device. When the key caps are placed very close to each other, even slight displacements are easily visible. Changes in positions may cause collisions of closely placed keys. A matter requiring particular accuracy is the attachment of the key caps to the key dome, since variations in the point of attachment affect the user""s feel of the keys, varying in a disturbing manner. It is difficult to position the key caps and the attachment precisely at the same point.
Keys of prior art are disclosed e.g. in U.S. patent publication Pat. No. 5,881,866 presenting key domes contained in a key pad and a key cap pressing the same by means of an actuator and being attached to the key pad at its edge portions. Also in this case, it is difficult to attach different keys always in the same position. One solution for the thickness of the keyboard of an electronic device, particularly a portable computer, is solved in U.S. patent publication Pat. No. 5,812,116, in which the attachment of the key caps is still high and difficult to assemble. Another keyboard construction is presented in U.S. patent publication Pat. No. 5,717,429, in which separate key caps are attached to a means corresponding to a key dome. One keyboard structure for an electronic device is also shown in U.S. patent publication Pat. No. 4,839,474, in which the key caps are fixed to a key pad by means of a flexible neck. The feel of the key is different when compared with a key dome.
It is an aim of the present invention to provide an improvement to the prior art; in particular, the aim is to achieve a compact keyboard with thin dimensions for an electronic device. The aim is to considerably facilitate the assembly and manufacture of the keyboard. The aim is to eliminate particularly the above-mentioned problems related to controlling the position and attachment of the key caps.
With the invention, considerable advantages are achieved particularly in the manufacture, which will become considerably easier. The need for a separate frame structure is eliminated, wherein the structure of the keyboard becomes lower, which makes thinner devices possible.
The device is particularly a PDA/CMT device, wherein the keyboard of the invention can be fitted between its two housings which can be closed and opened. The invention can be applied in the keyboards of both the PDA and the CMT user interfaces. A particular advantage is achieved in that the keyboard can be easily installed and replaced, wherein the installation of various keyboard versions is possible without replacing the housings or frame structures. Furthermore, the connection of the keyboard assembly to the device can be deferred to the final stage of production, which will facilitate the manufacture of different versions.
A particular advantage is achieved in that the assembly of single key caps is avoided, wherein position and attachment errors are considerably reduced and even totally eliminated. After this, it is no longer necessary to manufacture single, separate key caps for separate installation. Thanks to the method, the same uniform feel can be obtained for all the keys of the keyboard. The manufacturing technique also has the advantage that when blanks of the same assembly are used, it is easy to form different, even single configurations for keys by cutting. It is obvious that when the method is used, it is particularly easy to implement modifications in the design of the key caps. The whole space between the key caps is available for even large cap structures, wherein no frame structures need to be placed therebetween. By means of the method, the spaces are formed precisely according to the desired dimensions.
The invention is based on the idea that a key pad used as a uniform base is first connected with a uniform plate-like piece in which separate key switches, more precisely their key caps, are formed first after this by cutting. The parts to be cut off from the piece represent the key caps, and these parts remain, even when cut, attached to their base, wherein the installation of separate caps is avoided. The invention is also based on the idea that the cutting is performed by precise laser cutting by removing the material layer by layer. In this connection, so-called ablation is applied to improve the cutting result, to avoid drawbacks caused by heating and melting of the material during the cutting. The energy of the laser beam is only used to cause breaking of molecule bonds. To accelerate the cutting, the key caps are preferably placed very close to each other, wherein the quantity of the material to be removed is considerably reduced and the spaces do not need to be covered by other structures. In the method, the material can be removed in cut pieces, wherein also in this case e.g. a frame structure can be placed between the key caps, if necessary.
It should be noted that the presented laser apparatuses are known as such from other uses. For example, U.S. patent publication Pat. No. 6,008,468 should be mentioned, in which also a mask arrangement is used for manufacturing net-like pieces. Furthermore, U.S. patent publication Pat. No. 5,066,357 is known, in which laser cutting is applied to form circuits on a substrate. In laser cutting, the beam energy, scanning rate, scanning times, radiation wavelength, scanning frequency, the thickness of the material layer to be removed, and other functional parameters used for each material and for the desired final result are thus prior art known by anyone skilled in the art, in which also normal experimental and test runs can be applied for comparison and testing. Yet another example of a known laser apparatus for cleaning the surface of the substrate is presented in U.S. patent publication Pat. No. 5,669,979.